The present invention aims at providing a transformer (18) or a wind power generating facility (14) capable of improving cooling performance. In order to achieve the purpose, the present invention adopts the technical scheme characterized in that: the transformer (18) is contained in the wind power generating facility (14), and comprises a transformer body (1) and a natural cooling type radiator (7) for release of heat of the transformer body (1). The transformer body (1) is accommodated in the wind power generating facility (14), and air outside the wind power generating facility (14) comes into contact with the natural cooling type radiator (7) to cool the same.